ATR and medulloblastoma: To address the potential involvement of endogenous DNA damage checkpoint activation and replication stress in human medulloblastomas, as indicated by the robust γH2AX marker and strong activation of the ATM‐Chk2 and ATR‐Chk1 signalling cascades on the clinical specimens (see Section 3.2 above), along with any relationship to HCMV, we turned to an established model of the human medulloblastoma cell lines D324 and DAOY, in some experiments complemented by direct infection with HCMV.